That's incredibly frustrating and unprofessional! Changing a critical detail like color without prior communication is a major breach of trust and can cause significant problems for your business. Here's a breakdown of the situation and how to handle it:

1. Trust Erosion: It shows the supplier doesn't respect your process, your specifications, or your partnership.
2. Business Disruption: The changed color might:
   • Render Your Inventory Useless: If it's for a specific product line or customer order.
   • Cause Customer Complaints/Returns: If end-users notice the difference.
   • Affect Brand Consistency: Especially critical if color is part of your brand identity.
   • Delay Production: If you need to source matching materials or halt assembly.
   • Increase Costs: Rework, scrap, expedited shipping for correct materials, potential refunds.
3. Lack of Transparency: Hiding the change is even worse than an accidental mistake. It suggests they knew it was wrong but didn't inform you.

Immediate Actions to Take:

1. Document Everything:

   • Take clear photos of the received goods showing the incorrect color.
   • Find the original purchase order (PO), contract, or specification sheet detailing the correct color (e.g., Pantone number, physical sample, exact description).
   • Gather all previous communication (emails, messages) confirming the agreed-upon color.
   • Note the date you received the shipment and the PO number.

2. Contact the Supplier Immediately & Firmly:

   • Call First: Get them on the phone immediately. Be calm but direct and firm.
   • State the Facts: "I received shipment [PO #] dated [Date]. The color of [Product Name] is incorrect. It should be [Specify Correct Color, e.g., Pantone 1234 C], but it appears to be [Describe Incorrect Color]."
   • Demand Explanation: "Why was the color changed without any prior notification or approval from us?"
   • State the Impact: "This change has caused significant disruption: [Briefly explain impact - e.g., delays production, requires rework, risks customer returns, scrapes inventory]."
   • Demand Corrective Action: "We require the following immediately:"
     • Replacement: "Send the correct color material/shipping immediately, at your cost."
     • Return: "Arrange for pickup and return of the incorrect material at your cost."
     • Compensation: "Provide compensation for [Specify costs: expedited shipping, rework labor, scrap value, potential customer refunds, etc.]."
     • Explanation: "Provide a detailed written explanation of why the change was made and why we weren't informed."
     • Prevention: "Explain your process to ensure this never happens again."

3. Put it in Writing (Follow Up the Call):

   • Send a detailed email summarizing the phone call:
     • Reference the PO/shipment.
     • State the issue (incorrect color).
     • Attach photos and reference the original spec.
     • List your demands (replacement, return, compensation, explanation, prevention plan).
     • Set a clear deadline for their response and action (e.g., "We require your written response and plan of action by [Date]").
     • State the consequences of inaction (e.g., "Failure to resolve this satisfactorily may result in termination of our contract and pursuit of all available remedies for damages incurred.").

Next Steps & Considerations:

1. Review Your Contract/PO Terms:

   • Does it specify requirements for change notifications?
   • What are the remedies for non-conforming goods?
   • What are the consequences for breach of contract? (This strengthens your position).

2. Assess the Damage:

   • Can you use the incorrect material for a less critical purpose?
   • What are the actual costs incurred (labor, materials, shipping, lost sales)?
   • How urgently do you need the correct material?

3. Evaluate the Supplier's Response:

   • Apology & Accountability: Do they take full responsibility? A good response includes a sincere apology and ownership.
   • Action Plan: Is their plan concrete, timely, and addresses all your demands? Is the compensation fair?
   • Prevention: Is their explanation for the failure believable? Is their proposed prevention process robust?
   • Attitude: Are they cooperative and trying to fix it, or defensive and dismissive?

4. Decide on the Relationship:

   • First Offense (with excellent response): You might give them a chance if they fix everything perfectly and implement a foolproof prevention plan. But trust is damaged.
   • Pattern of Issues/Poor Response: This is a major red flag. Seriously consider finding a new supplier. Reliability and communication are non-negotiable. The cost and risk of dealing with them again may outweigh any benefit.

5. Mitigate Your Risk Going Forward:

   • Clear Specifications: Ensure your POs/specs are crystal clear on color (include physical samples you keep and reference, or precise color codes).
   • Contract Clauses: Explicitly require written approval for any changes to specifications, including color, before production or shipment.
   • Supplier Audits/Vendor Management: Implement processes to vet suppliers and monitor performance.
   • Incoming Inspection: Strengthen your quality control checks, especially for critical attributes like color.
   • Communication Protocols: Establish clear points of contact and communication channels for change notifications.

Key Takeaway: This supplier's behavior is unacceptable. Address it firmly, document everything, demand full resolution (including compensation for your losses), and seriously reassess whether they are a reliable partner for your future needs. Don't let them off the hook – their lack of communication caused you harm.